Merge pull request #30 from axieinfinity/merge/release/v0.1.0-feature…

…/math

chore(`math`): merge from `release/v0.1.0`

test/transfers/LibNativeTransfer.t.sol

@@ -25,7 +25,7 @@ contract LibNativeTransferTest is Test {
     // Transferring to msg.sender can fail because it's possible to overflow their ETH balance as it begins non-zero.
     if (recipient.code.length > 0 || uint256(uint160(recipient)) <= 18 || recipient == msg.sender) return;
 
-    amount = bound(amount, 0, address(this).balance);
+    amount = _bound(amount, 0, address(this).balance);
     LibNativeTransfer.transfer(recipient, amount, gas);
 
     assertEq(recipient.balance, amount);